Function spawn

src/bridge/sessionRunner.ts:250–546

(opts: SessionSpawnOpts, dir: string)

export function createSessionSpawner(deps: SessionSpawnerDeps): SessionSpawner {
  return {
    spawn(opts: SessionSpawnOpts, dir: string): SessionHandle {
      // Debug file resolution:
      // 1. If deps.debugFile is provided, use it with session ID suffix for uniqueness
      // 2. If verbose or ant build, auto-generate a temp file path
      // 3. Otherwise, no debug file
      const safeId = safeFilenameId(opts.sessionId)
      let debugFile: string | undefined
      if (deps.debugFile) {
        const ext = deps.debugFile.lastIndexOf('.')
        if (ext > 0) {
          debugFile = `${deps.debugFile.slice(0, ext)}-${safeId}${deps.debugFile.slice(ext)}`
        } else {
          debugFile = `${deps.debugFile}-${safeId}`
        }
      } else if (deps.verbose || process.env.USER_TYPE === 'ant') {
        debugFile = join(tmpdir(), 'claude', `bridge-session-${safeId}.log`)
      }

      // Transcript file: write raw NDJSON lines for post-hoc analysis.
      // Placed alongside the debug file when one is configured.
      let transcriptStream: WriteStream | null = null
      let transcriptPath: string | undefined
      if (deps.debugFile) {
        transcriptPath = join(
          dirname(deps.debugFile),
          `bridge-transcript-${safeId}.jsonl`,
        )
        transcriptStream = createWriteStream(transcriptPath, { flags: 'a' })
        transcriptStream.on('error', err => {
          deps.onDebug(
            `[bridge:session] Transcript write error: ${err.message}`,
          )
          transcriptStream = null
        })
        deps.onDebug(`[bridge:session] Transcript log: ${transcriptPath}`)
      }

      const args = [
        ...deps.scriptArgs,
        '--print',
        '--sdk-url',
        opts.sdkUrl,
        '--session-id',
        opts.sessionId,
        '--input-format',
        'stream-json',
        '--output-format',
        'stream-json',
        '--replay-user-messages',
        ...(deps.verbose ? ['--verbose'] : []),
        ...(debugFile ? ['--debug-file', debugFile] : []),
        ...(deps.permissionMode
          ? ['--permission-mode', deps.permissionMode]
          : []),
      ]

      const env: NodeJS.ProcessEnv = {
        ...deps.env,